Collaborative Research: Testing Source vs. Crustal Processing in High-Mg# Arc Magmas by Os-O-He-Olivine Systematics

合作研究：高镁测试来源与地壳处理

• 批准号: 1921643
• 负责人: Elisabeth Widom
• 金额: $ 21.26万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1921643&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Source; vs.

'Convergent plate margins' are major interfaces of the solid Earth geochemical cycle that are fundamental to the formation and maintenance of habitable Earth. At convergent plate margins, a lithospheric plate consisting of the Earth's crust and uppermost mantle is drawn - or subducted - beneath another lithospheric plate. At around 80-140 kilometers depth, the subducted plate releases material rich in climate-active volatile elements (H2O, halogens) and 'recycles' it back to the Earth's surface via the activity of volcanoes aligned in arcs. Such arcs form the 'Pacific Ring of Fire', which is renowned for volatile-rich, devastating eruptions of silicic magmas that can cause deadly climate perturbations (e.g. Tambora 1815) and tsunamis (e.g. Krakatoa 1883, 2018), and that are a permanent major threat to human habitation on the densely populated Earth. Thus, understanding how material cycling leads to silicic, explosive arc volcanism remains a theme at the core of geoscience research. A particular challenge when studying subduction recycling is that it takes place deep in the Earth's interior (between a few and 200 km) and thus cannot be observed directly. Scientists therefore rely on indirect observations obtained from components in magmas (e.g. olivine and spinel crystals) that carry information on processes occurring at many kilometers depth within the Earth. Two US-based women (one with a disability) plan to collect such information from volcanic rocks erupted from young Mexican volcanoes, in collaboration and exchange with national and international colleagues from the US, Mexico, Scotland and France. The project will train graduate and undergraduate students with the goal to promote diversity. K-12 teachers will be engaged in order to transfer the new research results into the Earth Science curriculum for middle and high school students, and the general public will be informed at regular annual Open Days.This project focuses on olivine and its inclusions of Cr-spinel from mafic to silicic magmas in the Trans-Mexican Volcanic Belt (TMVB), a major subduction zone that is well-known for its high potential for catastrophic volcanic eruptions. Many studies propose that the silicic magmas gain their deadly explosive power through melt processing in the 45 km thick continental crustal basement on the which the TMVB is constructed. However, some studies suggest that the composition of olivine crystals contained in these magmas is inconsistent with this hypothesis. Remarkably, olivines from the central TMVB have delta18O and 3He/4He isotope signals that suggest that their host magmas were primarily formed in the mantle below the crustal basement, where they became silicic through incorporation a large amount of subducted slab material. In this project we will further test these two contrasting hypotheses by obtaining additional 187Os/188Os isotope data from olivine and bulk rocks that have been carefully selected from key locations in the central (Popocatepetl and Sierra Chichinautzin) and eastern (Serdan basin) TMVB, as well as from the rear-arc region where magmas are not significantly affected by subduction. The Os-He-O isotope ratios will be combined with data on the composition of olivine and included Cr-spinels to infer the temperatures and oxygen fugacity of olivine crystallization, enabling a holistic model on the mode of silicic melt formation. Overall, the project will provide new constraints on the connectivity between slab subduction and arc volcanism and its role in regulating the long-term evolution and maintenance of habitable Earth.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

“收敛板边缘”是固体地球地球化学循环的主要界面，这是对可居住地的形成和维护至关重要的。在收敛板边缘，在另一个岩石圈板下方画出了由地壳和最上层的岩石圈板。在大约80-140公里的深度下，俯冲板释放了富含气候活性挥发性元件（H2O，卤素）的材料，并通过在ARC中排列的火山活性来“回收”它回到地球的表面。这种弧形构成了“太平洋火环”，它以易变的，毁灭性的硅质岩浆爆发而闻名，可能会引起致命的气候扰动（例如，坦博拉1815年）和海啸（例如，坦博拉（Tambora）1815）（例如，克拉卡托（Krakatoa）1883，2018），以及对人类永久性的人类习惯的永久性威胁。因此，了解物质循环如何导致硅质，爆炸性的弧形火山主义仍然是地球科学研究核心的主题。研究俯冲回收时的一个特殊挑战是，它发生在地球内部（几至200公里之间），因此无法直接观察到。因此，科学家依赖于从岩浆（例如橄榄石和尖晶石晶体）中的组成部分获得的间接观察，这些观察结果携带有关地球内许多公里深度的过程的信息。两名美国妇女（一名残疾人）计划从墨西哥火山的年轻火山岩中收集此类信息，并与美国，墨西哥，苏格兰和法国的国家和国际同事合作和交流。该项目将培训毕业生和本科生，以促进多样性。 K-12教师将订婚，以便将新的研究结果转移到中学和高中生的地球科学课程中，并将在常规的年度开放日内通知公众。该项目重点介绍Olivine及其CR Spinel的CR及其从镁铁质的含量到硅质岩浆到跨墨西哥式燃料的硅胶（TMVB），以供货物范围（TMVB），这是一个众所周知的，是众所周知的，这是该地区的众所周知的，这是众所周知的。爆发。许多研究表明，硅质岩浆通过在构造TMVB的45公里厚的大陆地壳地下融化加工中获得致命的爆炸能力。但是，一些研究表明，这些岩浆中包含的橄榄石晶体的组成与该假设不一致。值得注意的是，来自中央TMVB的橄榄石具有Delta18O和3HE/4HE同位素信号，这些信号表明它们的宿主岩浆主要是在​​地下甲壳地下室下方的地幔中形成的，在那里它们通过掺入大量的俯冲板材料而变成了硅胶。在这个项目中，我们将通过从中央（PopocatePetl和Sierra Chichinautzin）和Eastern（Serdan Basin）TMVB以及磁场不显着的Silectift Incorctioncy的情况下，从中央（PopocatePetl和Sierra Chichinautzin）和Eastern（Serdan basin）中心仔细选择，进一步测试了这两个对比的假设，这些假设是从橄榄石和大块岩石中获取其他187OS/188OS同位素数据。 OS-HE-O同位素比将与有关橄榄石组成的数据结合使用，并包括CR型螺旋体，以推断橄榄石结晶的温度和氧散性，从而在硅质熔体形成模式下实现了整体模型。总体而言，该项目将对平板俯冲和电弧火山弧之间的连通性提供新的限制，及其在规范长期演变和维持可居住地球的作用。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来支持的。